being able to restrict web use to certain times for certain mac addressesi have a cheap yet reliable modem/router which allows me to do this with manual entries on the routersurely this is something which could be implemented without too much back end engineering?

AMEN!! I would like to be able to configure things so that my settings automatically changed after 10:30. SOmetimes i want to go to bed before my kids without worrying that what they are allowed to use until bedtime is not used AFTER that.

Then do so. But if you want an entirely remote service to handle this for you, then you are barking up the wrong tree. There are lots of requests for such tools - you are hardly alone. They are perennial favourites of the forum and the Idea Bank.

All sorts of routers allow for time-based restrictions, and the Netgear LPC offering will do exactly that with OpenDNS filtering. Because OpenDNS cannot possibly kick users off an existing connection and flush all caches for you (I'm sure somebody would, if you gave them remote administrative control over all the devices in your network), nor is it likely that it is economically feasible to provide that much more processor time and storage space to such a venture - although there may be incentive in the future as people delegate their privacy and security to various entities as "cloud services" become the normal thing again, until it becomes the old thing again.

This is why all sorts of things people request OpenDNS to do are not done: because they deal with properties of your local network and machines - your LAN. And OpenDNS is almost peculiarly non-invasive, a bit by nature and a bit by the apparent corporate philosophy. But they partnered with some router vendors, and Netgear produced firmware for some of its routers which works with software you can use for this sort of task and others parents look for. And no updater - it's built in.